Time for pulse traversal through slabs of dispersive and negative (ϵ\epsilon, μ\mu) materials

The traversal times for an electromagnetic pulse traversing a slab of dispersive and dissipative material with negative dielectric permittivity ($\epsilon$) and magnetic permeability ($\mu$) have been calculated by using the average flow of electromagnetic energy in the medium. The effects of bandwidth of the pulse and dissipation in the medium have been investigated. While both large bandwidth and large dissipation have similar effects in smoothening out the resonant features that appear due to Fabry-P\'{e}rot resonances, large dissipation can result in very small or even negative traversal times near the resonant frequencies. We have also investigated the traversal times and Wigner delay times for obliquely incident pulses and evanescent pulses. The coupling to slab plasmon polariton modes in frequency ranges with negative $\epsilon$ or $\mu$ is shown to result in large traversal times at the resonant conditions. We also find that the group velocity mainly contributes to the delay times for pulse propagating across a slab with n=-1. We have checked that the traversal times are positive and subluminal for pulses with sufficiently large bandwidths.Comment: 9 pages, 9 figures, Submitted to Phys. Rev.

Complete controllability of quantum systems

Sufficient conditions for complete controllability of $N$-level quantum systems subject to a single control pulse that addresses multiple allowed transitions concurrently are established. The results are applied in particular to Morse and harmonic-oscillator systems, as well as some systems with degenerate energy levels. Morse and harmonic oscillators serve as models for molecular bonds, and the standard control approach of using a sequence of frequency-selective pulses to address a single transition at a time is either not applicable or only of limited utility for such systems.Comment: 8 pages, expanded and revised versio

Store choice behavior in food and grocery retailing in India an empirical analysis

Shopping for food and grocery products has witnessed a paradigm shift in Indian retail market with the changes in consumer buying behaviour driven by strong income growth, changing lifestyles and favourable demographic patterns. But the very fast changing trends in consumption patterns, food and eating habits of consumers have contributed immensely to the growth and development of 'Western' format typologies such as convenience stores, discount stores, super markets, and hyper markets. The present study is exploratory in nature to identify and examine the determinant attributes influencing consumer behaviour towards super market store format choice decisions in the fast growing food and grocery retailing in India. The population of the study is confined to the retail customers (7.5 crore) ofAndhra Pradesh state and sampling sources are twin cities of Secunderabad and Hyderabad (58 Lakh population). The 'mall intercept' survey method is adopted to study the attitudes and opinions of retail customers through questionnaires. The descriptive statistical tools (like mean, standard deviation and median) and inferential statistical tools like Factor Analysis, Chi-Square, ANOVA, Correlation, and Multiple regressions are used to test the formulated hypotheses and validate the model. The study has found significant association between shopper attributes and store format choice decisions. The findings revealed that merchandise, customer service, location and atmospheric related store attributes are affecting the store format choice behaviour. The study has discussed various academic and managerial implications for retail industry in general and food & grocery in particular

Morphological structures and drug release effect of multiple electrospun nanofibre membrane systems based on PLA, PCL, and PCL/Magnetic nanoparticle composites

Biopolymers are good carrier materials in relation to efficient release sustainability for encapsulated drugs. In particular, electrospun polymer/composite fibre membranes can offer greater benefits owing to their competitive release features as well as large specific surface areas. In this study, multiple electrospun nanofibre membrane systems were utilised including different material systems such as poly(lactic acid) (PLA), poly(ε-caprolactone) (PCL), and PCL/magnetic nanoparticle (MP) composites loaded with tetracycline hydrochloride (TCH) as a therapeutic compound for their potential use in drug delivery applications. Such electrospun nanofibres were investigated to understand how composite constituents could tailor surface morphology for drug release control and biodegradation effect of PCL electrospun nanofibers on a long term for different drug release systems. Fibre diameter appeared to be decreased considerably with the addition of TCH drug. It was also evident that average fibre diameter was reduced when embedding MPs owing to the enhancement of solution conductivity. The encapsulation of TCH drug was found to be effective, as evidenced by Fourier transform infrared (FTIR) spectra. Thermogravimetric analysis (TGA) data revealed no significant change in the thermal stability of PCL with the inclusion of TCH and MPs. However, the use of TCH to PLA delayed the thermal degradation. Glass transition temperature (TQ) and melting temperature (TM) of PCL were decreased with the inclusion of MPs and TCH. The degree of crystallinity (XC) for PCL diminished when incorporated with MPs. Additional TCH to PLA, PCL, and PCL/MP nanocomposites resulted in a moderate decrease in (XC). TCH might be dispersed in an amorphous state within nanofibre membranes. Over the short-term periods, it was clearly seen that TCH release from PCL nanofibre membranes was higher as opposed to PLC/MP and PLA counterparts. On the contrary, such a drug release from PLC membranes became relatively slow owing to its high (XC). Further, the mass loss results were consistent with those obtained from in vitro drug release. Overall, TCH release kinetics of PCL/TCH nanofibre membranes were better estimated by Zeng model as opposed to PLA/TCH counterparts

Silicon Nitride Plates for Turbine Blade Application: FEA and NDE Assessment

Engine manufacturers are continually attempting to improve the performance and the overall efficiency of internal combustion engines. The thermal efficiency is typically improved by raising the operating temperature of essential engine components in the combustion area. This reduces the heat loss to a cooling system and allows a greater portion of the heat to be used for propulsion. Further improvements can be achieved by diverting part of the air from the compressor, which would have been used in the combustor for combustion purposes, into the turbine components. Such a process is called active cooling. Increasing the operating temperature, decreasing the cooling air, or both can improve the efficiency of the engine. Furthermore, lightweight, strong, tough hightemperature materials are required to complement efficiency improvement for nextgeneration gas turbine engines that can operate with minimum cooling. Because of their low-density, high-temperature strength, and thermal conductivity, ceramics are being investigated as potential materials for replacing ordinary metals that are currently used for engine hot section components. Ceramic structures can withstand higher operating temperatures and other harsh environmental factors. In addition, their low densities relative to metals helps condense component mass (ref. 1). The objectives of this program at the NASA Glenn Research Center are to develop manufacturing technology, a thermal barrier coating/environmental barrier coating (TBC/EBC), and an analytical modeling capability to predict thermomechanical stresses, and to do minimal burner rig tests of silicon nitride (Si3N4) and SiC/SiC turbine nozzle vanes under simulated engine conditions. Furthermore, and in support of the latter objectives, an optimization exercise using finite element analysis and nondestructive evaluation (NDE) was carried out to characterize and evaluate silicon nitride plates with cooling channels

Nano-Engineered Environment for Nerve Regeneration: Scaffolds, Functional Molecules and Stem Cells

One of the most complex systems in the human body is the nervous system, which is divided into the central and peripheral nervous systems. The regeneration of the CNS is a complex and challenging biological phenomenon hindered by the low regenerative capacity of neurons and the prohibition factors in response to nerve injuries. To date, no effective approach can achieve complete recovery and fully restore the functions of the nervous system once it has been damaged. Developments in neuroscience have identified properties of the local environment with a critical role in nerve regeneration. Advances in biomaterials and biomedical engineering have explored new approaches of constructing permissive environments for nerve regeneration, thereby enabling optimism with regard to nerve-injury treatment. This article reviews recent progress in nanoengineered environments for aiding nerve-injury repair and regeneration, including nanofibrous scaffolds, functional molecules, and stem cells.postprin

Correcting the quantum clock: conditional sojourn times

Can the quantum-mechanical sojourn time be clocked without the clock affecting the sojourn time? Here we re-examine the previously proposed non-unitary clock, involving absorption/amplification by an added infinitesimal imaginary potential($iV_{i}$), and find it {\it not} to preserve, in general, the positivity of the sojourn time, conditional on eventual reflection or transmission. The sojourn time is found to be affected by the scattering concomitant with the mismatch, however small, due to the very clock potential($iV_{i}$) introduced for the purpose, as also by any prompt scattering involving partial waves that have not traversed the region of interest. We propose a formal procedure whereby the sojourn time so clocked can be corrected for these spurious scattering effects. The resulting conditional sojourn times are then positive definite for an arbitrary potential, and have the proper high- and low-energy limits.Comment: Corrected and rewritten, RevTeX, 4 pages, 2 figures (ps files) include

Morpho-Agronomic Diversity in Pole-Type Common Bean (Phaseolus vulgaris L.) Landraces from Lushai Hills of North-East India

The present study was based on morphological and agronomical characterization of 23 pole-type common bean (Phaseolus vulgaris L.) landraces collected from Lushai hills of North-East India. Extensive variation in plant and seed traits was found in 16 morphological and agronomical characters. Cluster analysis based on Euclidean distance grouped the genotypes into five main branches, reflecting their growth type and reproductive traits. Significant positive or negative correlation was observed among important traits. Principal component analysis was used for assessing patterns of variation by accounting for all the 10 quantitative and six qualitative variables together. Ordination among accessions showed that the first five principal components had Eigen values greater than one, and cumulatively accounted for 72% of the variation. Characterization based on quantitative and qualitative traits enabled separation of accessions into various groups representing landraces with distinct characters